Current telecommunications platforms (such as cell phones) rely on a series of radiofrequency (RF) and intermediate frequency (IF) filters in order to isolate the desired communications band or channel from the crowded and noisy background. Currently, surface acoustic wave (SAW), bulk acoustical wave (BAW), film bulk acoustic resonator (FBAR) and ceramic filters are the devices of choice. However, in general, these filters are large, bulky, and expensive discrete packaged components that cannot be integrated with the rest of the transceiver architecture. While the front-end module of the transceiver can and does continue to miniaturize with improving lithographic processes and designs, the filter stands as the bottleneck to a truly integrated radio package.
More and more, a greater number of communications standards (GSM, CDMA, PCS, European/US, UMTS) and features (WiFi, cameras) are being incorporated into a single handset. While this allows for truly global communications, it comes at the cost of a larger and more power-hungry device. Adding more bands and modes means that more and more discrete packages are added onboard, with corresponding increases in overall board size and power consumption due to package-to-package signal losses.
Therefore, a need exists for a type of filter that is small in size, utilizes minimal power and can be integrated with other discrete electrical elements. In addition, a need exists for banks of these types of filters as well as switches. Moreover, a need exists for filter banks capable of handling multiple bands or channels. Further, the capability of switching between the bands and uplink or downlink channels is also needed.